Absorbent article with surface structure

ABSTRACT

There is disclosed an absorbent article including: a surface structure having a liquid-permeable surface sheet located on a liquid-receiving side; a back sheet; and an absorbent core sandwiched between the surface structure and the back sheet. In an area including at least a centerline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses and ridges extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction. The ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape. The surface structure thus curved can fit the shape of a crotch. Therefore, the liquid is hard to flow in the transverse direction to prevent the leakage.

This application is a divisional application of U.S. patent applicationSer. No. 09/531,808, filed Mar. 21, 2000 now U.S. Pat. No. 6,436,081issued Aug. 20, 2002 to Wada et al.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an absorbent article such as adisposable diaper, a pad for the incontinence of urine or a sanitarynapkin and, more particularly, it relates to an absorbent articleincluding a surface structure having an excellent fittingness on a body.

2. Related Art

The absorbent article of the prior art such as the disposable diaper,the pad for the urinary incontinence or the sanitary napkin generallyincludes: a liquid-permeable top sheet disposed on the liquid-receiving,inner side; a liquid-impermeable back sheet disposed on the outer side;and an absorbent core made of pulp and a highly absorbent polymer (orsuper absorbent polymer: SAP) and sandwiched between the two sheets.

In such an absorbent article, a structure has been investigated forimproving the fittingness on a urinary organ and thereabout, whenapplied to a crotch, to prevent excreted liquid such as urine ormenstrual blood from leaking transversely. For example, there has beenpracticed a structure, in which a relatively bulky cushion layer made ofa hydrophilic fiber layer is disposed on the liquid-receiving side ofthe absorbent core, or a structure in which an absorbent material layersmaller than the absorbent core is disposed on the liquid-receiving sideof the absorbent and such a cushion layer as above is further disposedon the absorbent material layer. In another structure, gathers forpreventing the transverse leakage are disposed on two side edges of theabsorbent core.

However, the aforementioned absorbent article provided with the cushionlayer cannot cover the individual differences in the shape of the crotchreliably at all times. Especially, the disposable diaper or the pad forthe urinary incontinent for taking care of old people frequently failsto fit the crotch. This is because the old people are seriouslydifferent among the individuals in the width of the crotch, in the fleshof the crotch, abdomen or hip or in the flabbiness or wrinkles of theskin, as compared with infants. If the absorbent article fails to fitthe crotch, the excreted liquid will easily leak along the skin to theoutside of the absorbent article to wet the wears or bedclothes. Thisproblem is more serious for the old people who excrete far more liquidfor one urination than the infants. When such an absorbent articleunfitted for the crotch is worn, moreover, irregular wrinkles are formedon the liquid-receiving side of the absorbent article to make it harderfor the absorbent article to absorb the excreted liquid.

Against these problems, there exists an absorbent article which iscurved to fit the crotch by providing transverse leakage preventinggathers on two side edges of an absorbent core so that the absorbentcore may follow the gathers. However, even in this absorbent article,because the central portion of the absorbent core is less curved thanthe side edges thereof, the absorbent core is difficult to fit the wholecrotch, thereby to leave gaps between the absorbent core and the crotch.As a result, a large amount of excreted liquid may move transverselythrough the gaps so that its leakage cannot be prevented by thetransverse leakage preventing gathers.

SUMMARY OF THE INVENTION

The present invention is to solve the problems of the prior art thus fardescribed and has an object to provide an absorbent article in which asurface structure disposed on the liquid-receiving side easily fits thecrotch, the urinary organ or the inguinal region.

Another object of the invention is to provide an absorbent article whichis so curved as to easily fit the crotch of the wearer thereby toprevent the transverse leakage of the excreted liquid.

According to an aspect of the invention, there is provided an absorbentarticle comprising: a surface structure having a liquid-permeablesurface sheet located on a liquid-receiving side; a back sheet; and anabsorbent core sandwiched between the surface structure and the backsheet, wherein, in an area including at least a centerline extending ina longitudinal direction of the absorbent article, the surface sheet iscorrugated to form recesses and ridges extending in the longitudinaldirection and alternating with each other in a transverse directionperpendicular to the longitudinal direction, and the ridges are given anelastically shrinking function in the longitudinal direction at least attheir crests or vicinities thereof so that the surface structure isformed into a curved shape.

With the surface structure of the absorbent article of the invention,the surface sheet constructing the surface structure elastically shrinksin the longitudinal direction so that the surface structure is curved.As a result, the absorbent article is curved in its entirety so that theliquid-receiving side easily fits the crotch, the abdomen or the back(or hip). Therefore, the excreted liquid can be quickly absorbed by theabsorbent article while being prevented from leaking transversly. Togive the elastically shrinking function, preferably, elastic membersextending in the longitudinal direction are attached to the crests ofthe ridges of the surface sheet.

Moreover, because the ridges thus formed have degrees of freedom againstthe vertical and horizontal pressures i.e., because they can be flexiblydeformed, the ridges can fit the roughness of the urinary organ, thecrotch or the inguinal region. In other words, the surface structurecomes into contact with the wearer's body to have a larger contact areafor eliminating gaps between the absorbent article and the wearer'sbody. As a result, the excreted liquid is prevented from flowingtransversely in such gaps and its leakage is further reduced.

Preferably, the surface structure further includes a liquid-permeablesupport sheet located between the surface sheet and the absorbent core,and the support sheet is bonded to the surface sheet at an interval inthe transverse direction to thereby form the recesses. In this case,more preferably, a cushion layer is provided inside of the ridges suchthat the cushion layer is sandwiched between the surface sheet and thesupport sheet.

Preferably, ridges in a center region including the longitudinallyextending centerline are different in height from other ridges in twoside regions outside of the center region.

Preferably, cover sheets are provided to cover longitudinal end portionsof the ridges.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a partially sectional, perspective view showing an absorbentarticle according to a first embodiment of the invention;

FIG. 2 is a sectional view of the absorbent article shown in FIG. 1;

FIG. 3 is an explanatory view showing a curved state of a surfacestructure of the invention;

FIG. 4 is a partially sectional, perspective view showing an absorbentarticle according to a second embodiment of the invention;

FIG. 5 is a sectional view showing an absorbent article according to athird embodiment of the invention;

FIG. 6 is a sectional view showing an absorbent article according to afourth embodiment of the invention;

FIG. 7 is a top plan view showing an example in which a disposablediaper is constructed of the absorbent article of the invention;

FIG. 8 is a perspective view showing an absorbent article according to afifth embodiment of the invention;

FIG. 9 is a (transversely) sectional view of the absorbent article ofFIG. 8; and

FIG. 10 is a (longitudinally) sectional view of the absorbent article ofFIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a partially sectional, perspective view showing an absorbentarticle according to a first embodiment of the invention; FIG. 2 is asectional view of the absorbent article of the invention; and FIG. 3 isan explanatory view showing a state in which a surface structure iscurved. In the following, a direction X is a transverse (or widthwise)direction of the absorbent article, and a direction Y is a longitudinal(or lengthwise) direction of the absorbent article.

As shown in FIGS. 1 and 2, an absorbent article 1 is backed on a backside of an absorbent core 2 with a back sheet 3 and is surfaced on aliquid-receiving side of the absorbent core 2 with a surface structure4. This surface structure 4 includes a surface sheet 5 and a supportsheet 6, and these surface sheet 5 and support sheet 6 and the backsheet 3 are adhered together with an adhesive such as hot melt adhesivein a peripheral region A where no absorbent core 2 is present. When thesurface sheet 5, the support sheet 6 and the back sheet 3 containthermoplastic fibers, they may be thermally fused together in theaforementioned peripheral region A. Alternatively, it may be possiblethat only the support sheet 6 and the back sheet 3 are bonded (adheredor fused) together in the peripheral region A, while the surface sheet 5is bonded to the support sheet 6 at a position inside of the peripheralregion A (i.e. at a positon where the absorbent core 2 is present).

The absorbent core 2 is constructed by enveloping either pulverized pulpor a mixture of pulverized pulp and highly absorbent polymer (or superabsorbent polymer: SAP) with an absorbent sheet such as tissue paper.The SAP can be made of polyacrylic acid, sodium polyacrylate,polyacrylamide, polyacrylonitrile, polyvinyl alcohol, an additionalpolymer of maleic anhydride, a polyether, a condensed polymer, apolysaccharide such as starch or cellulose, a protein such as collagen,or the like. Examples of the SAPs include: a cross-linked compound ofsodium polyacrylate, a graft copolymer of starch having sodiumpolyacrylate or a graft copolymer of cellulose having polyacrylonitrilechains. The back sheet 3 may be liquid-impermeable and made of, forexample, an olefin resin sheet. When the absorbent article 1 is used asa disposable diaper or sanitary napkin, the back sheet 3 is preferablymade gas-permeable. However, the back sheet 3 of the absorbent article 1of the invention may be made liquid-permeable, if it is used to be worninside another absorbent material in which excessive liquid willpermeate and will be absorbed.

The aforementioned surface sheet 5 and support sheet 6 composing thesurface structure 4 are preferably made of a point-bond, air-through,spun-bond or spun-lace non-woven fabric. This non-woven fabric is formedof, for example, hydrophilized hydrophobic fibers or hydrophilic fibers.The “hydrophilized hydrophobic fibers” as used herein means hydrophobicfibers subjected to hydrophilic treatment. In this hydrophilictreatment, a hydrophobic fiber is made hydrophilic by treating it with asurfactant; by chemically binding a chemical substance such as a monomeror a polymer having a hydrophilic group thereto; by subjecting it toplasma processing; by kneading it with a chemical substance having ahydrophilic group; or by treating its surface to have a profiledsection. The surface sheet 5 and support sheet 6 may be made of a resinfilm having a number of apertures. This resin film can be made ofpolyethylene (PE) or the like.

As in FIG. 2, the surface sheet 5 is bonded to the support sheet 6 at aninterval (or pitch distance) 7 p in the transverse direction. Thesebonded portions are designated by 7 a. By forming these bonded portions7 a, the surface sheet 5 is corrugated to have recesses 7 and ridges 8.That is, the surface sheet 5 is deformed to have the ridges (or bulges)8 rising toward the wearer, between the bonded portions 7 a. The ridges8 and the recesses 7 are extended in the longitudinal direction (or thedirection Y) to form a plurality of parallel rows. The bonding betweenthe surface sheet 5 and the support sheet 6 for forming the recesses 7can be performed by adhesion with an adhesive such as hot melt adhesive.Alternatively, the surface sheet 5 and the support sheet 6 may bethermally fused together when they contain thermoplastic fibers.

The bonded portions 7 a may be formed in longitudinally continuouslines. Alternatively, they may be formed to extend intermittently in thelongitudinal direction. For example, if an adhesive of the hot melt typeis applied to the surface of the support sheet 6 in a spiral pattern orthe like and the surface sheet 5 is adhered to the support sheet 6, thebonded portions 7 a can be formed intermittently in the longitudinaldirection as above. When the bonded portions 7 a are thus intermittentlyformed, the excreted liquid such as urine fed to the recesses 7 readilypenetrates from the bottoms of the recesses 7 into the absorbent core 2.

At the crests 8 t of the ridges 8, there are arranged elastic members10, each extending in the longitudinal direction. These elastic members10 are adhered to the inner side of the surface sheet 5, i.e., to theface of the surface sheet 5 on the side of the absorbent core 2, whilebeing elongated (or pulled and stretched) in the longitudinal direction.Therefore, after such adhesion, the surface sheet 5 longitudinallyshrinks at the crests 8 t owing to the elastically shrinking function ofthe elastic members 10, so that the whole surface structure 4 is curvedas shown in FIG. 3. As a result, the absorbent core 2 is also curved.

The elastic members 10 may be made of any elastic material such asnatural rubber, synthetic rubber or stretch non-woven fabric (i.e.,non-woven fabric having elasticity).

Here, the surface sheet 5 per se may be made of such stretch non-wovenfabric to have an elastically shrinking function in the longitudinaldirection. In this case, the elastic members 10 need not be provided tothe surface sheet 5. Therefore, the surface structure 4 can be easilymanufactured.

The height of the ridges 8, that is, the height size 8 h (as referred toFIG. 2) from the surface of the support sheet 6 to the crests 8 t of theridges 8 is preferably from 5 mm or more to 50 mm or less. Within thisrange, the liquid-receiving side of the absorbent article can fit thecrotch of a wearer, even if the absorbent article is used for takingcare of old people who are seriously different among the individuals inbody contours. More preferably, the height size 8 h is from 10 mm ormore to 30 mm or less.

In the surface structure 4, moreover, there may be provided a cushionlayer 9 of a hydrophilic material inside of the ridges 8, i.e., betweenthe surface sheet 5 and the support sheet 6, as shown in FIGS. 1 and 2.With this cushion layer 9, the elastcity of the ridges 8 is so enhancedthat the shape of the ridges 8 can be maintained securely when they comeinto contact with the wearer. In this case, therefore, the surfacestructure 4 will fit the crotch more closely. In stead of providing thecushions layer 9, however, the inside of the ridges 8 may be vacant.That is, the space between the surface sheet 5 and the support sheet 6may be left as clear gaps.

The hydrophilic material for the cushion layer 9 can be exemplified byvarious materials. For example, use can be made of hydrophilizedhydrophobic fibers of polyethylene, polypropylene, nylon or polyester,hydrophilized hydrophobic composite fibers of polyester andpolyethylene, or hydrophilic fibers such as rayon. As described before,the term “hydrophilized hydrophobic fibers” means hydrophobic fiberssubjected to hydrophilic treatment. Such fibers may be long fibers (orfilaments) prepared in the form of tow. Or else, use can be made of asplit yarn or strip-shaped materials, which are originally hydrophilicor originally hydrophobic but subjected to hydrophilic treatment. Thesplit yarn is produced by finely cutting a resin film into the net-likeshape, in which short fibers extend generally in one direction. Thestrip-shaped materials are produced by cutting a resin film or non-wovenfabric into strips. Alternatively, the material may be exemplified byeither a non-woven fabric, such as air-through non-woven fabric ofhydrophilic fibers or hydrophobic fibers subjected to hydrophilictreatment, which is bulky and has a low density, or a web of openedfibers having a relatively short length (e.g., hydrophilic fibers orhydrophobic fibers subjected to hydrophilic treatment). Preferably, thecushion layer 9 is bulky and readily permeable to liquid and can bereadily elastically recovered (or restored) from its pressurized state.Therefore, it is preferable that the cushion layer 9 has a density of0.4 g/cm³ or less and the fibers constituting the cushion layer 9 has afineness of 1 denier or more.

FIG. 4 is a perspective view showing an absorbent article 1B of a secondembodiment of the invention. In this absorbent article 1B, the ridges 8are made different. Hereinafter, the detailed description of theportions having the same constructions as those of the first embodimentwill be omitted by designating them by the common reference numerals.

In the embodiment shown in FIG. 4, the ridges 8 are made higher, asindicated by 8 a, in the vicinity of the central region and made lower,as indicated by 8 b, in the two side regions. Thus, the fittingness onthe crotch or urinary organ is further enhanced by the difference of theheight between the ridges 8 a and 8 b. In this case, the ridges 8 apreferably have a height of about 25 mm whereas the ridges 8 bpreferably have a height of about 15 mm. This embodiment may be modifiedsuch that the ridges are gradually lowered from ridges 8 c and 8 c inthe central region to ridges 8 d and 8 d in the two side regions.

On the contrary, the ridges 8 a in the vicinity of the central regionmay be made lower whereas the ridges 8 b in the two side regions may bemade higher. In this case, the ridges 8 a preferably have a height ofabout 5 mm whereas the ridges 8 b preferably have a height of about 15mm. Alternatively, the ridges 8 may be made gradually higher from thecentral region to the two side regions.

FIG. 5 is a sectional view showing an absorbent article 1C of a thirdembodiment of the invention. In FIG. 5, two elastic members 10 a and 10b are disposed at the crest 8 t of each ridge 8. Between two adjacentridges 8 and 8, on the other hand, two bonded portions 7 a and 7 a areprovided to form one recess 7. That is, in each recess 7, two continuousor intermittent lines of the bonded portions 7 a extend parallel to eachother.

FIG. 6 is a sectional view showing an absorbent article 1D of a fourthembodiment of the invention. In this embodiment, the ridge 8 is providedwith additional inner ridges.

In this absorbent article 1D, a second surface sheet 15 having a liquidpermeability is disposed on the inner side of the surface sheet 5 toform the inner ridges. Moreover, the elastic members 10 are disposed onthe inner side of the second surface sheet 15, not on the inner side ofthe first surface sheet 5, i.e., at the crests of the inner ridgesformed of the second surface sheet 15. With the second surface sheet 15,the cushioning properties of the surface structure 4 can be so enhancedwithout the aforementioned cushion layer 9 as to ensure a soft fittingon the crotch. In addition, the second surface sheet 15 functions as aliquid stopping layer for stopping liquid from flowing in the transversedirection. The second surface sheet 15 is formed of a resin film or ahydrophobic non-woven fabric having a plurality of apertures at a rateof aperture area of 30 to 50%, for example.

Here, the elastic members 10 may be disposed at the crests of the outerridges of the first surface sheet 5, as in the first embodiment. It isalso possible that the second surface sheet 15 per se is made of stretchnon-woven fabric having the elastically shrinking function in thelongitudinal direction while eliminating the elastic members 10. In thiscase, the first surface sheet 5 need not have the elastically shrinkingfunction.

FIG. 7 is a top plan view showing an open type disposable diaper withits liquid-receiving side being located on this side, as a specificembodiment of the absorbent article 1, 1B, 1C or 1D of the invention.

The disposable diaper, as constructed of the absorbent article of theinvention, has an intermediate portion 21 to be applied to the crotch ofa wearer; a front portion 22 to be applied to the abdomen thereof, and arear portion 23 to be applied to the hip thereof.

In the disposable diaper shown in FIG. 7, the back sheet 3 and thesupport sheet 6 are given an hour glass shape, and the absorbent core 2(indicated by dotted lines in FIG. 7) is also given an hour glass shape.The transversely constricted portions of those hour glass shapes providethe aforementioned intermediate portion 21. In the peripheral region Awhere the absorbent core 2 is not present, the support sheet 6 and theback sheet 3 are bonded to each other to secure the absorbent core 2therebetween.

In the disposable diaper shown in FIG. 7, the surface sheet 5 shown inFIGS. 1 and 2 is present only in the widthwise center on theliquid-receiving side to form the ridges 8 and the recesses 7. Thecushion layer 9 may or may not be disposed between the surface sheet 5and the support sheet 6.

The area where the ridges 8 and the recesses 7 are present is in arectangular shape extending from the front portion 22 through theintermediate portion 21 to the rear portion 23 in the longitudinaldirection and over two side regions 31 and 31 across a centerline 30 inthe transverse direction. That is, as shown in FIG. 7, the ridges 8 andthe recesses 7 are present in the area having a length almost equal tothat of the absorbent core 2 and a width almost equal to that of theintermediate portion 21 of the absorbent core 2. The area may bemodified variously according to the applications. In the disposablediaper of FIG. 7, the crests 8 t of the ridges 8 of the surface sheet 5are provided with the elastic members 10 for allowing the disposablediaper to be curved in its entirety by their elastic shrinking forces.

The elastic members 10 may be provided either all over the ridges 8 inthe longitudinal direction or only over the intermediate portion 21 inthe longitudinal direction. It may be also possible that not all butsome of the ridges 8 are provided with the elastic members 10.

In order to make the curvature of the surface structure proper for theinvention, the elastic members 10 are preferably provided over at least10% of the entire length L1 of the absorbent article 1. However, theelastic members 10 should not be limited to a continuous length of 10%or more but may be provided partially, for example, at two portions of5% or more of the entire length L1. The portion requiring the curvatureis different for targets of application. For a baby or child, forexample, it is preferable that not only the intermediate portion 21 butalso both the front portion 22 and the rear portion 23 are curved to fitthe round abdomen and hip. For an old wearer, the front portion 22 neednot be curved. Thus, the portion to be curved is properly adjusted.

The ridges 8 of the surface structure 4 are covered at their oppositeend portions 8 e and 8 e with cover sheets 11 and 11, as shown in FIG.7. Preferably, each cover sheet 11 has a width larger than that of thearea where the ridges 8 are formed, and is bonded to the support sheet 6with a C-shaped bonded portion 11 b to be opened toward the intermediateportion 21. That is, for forming a pocket, it is preferable that eachcover sheet 11 is not bonded to the support sheet 6 on the side of theintermediate portion 21.

When the excreted liquid moves along the ridges 8, it flows to the frontportion 22 or the rear portion 23 of the absorbent article 1 and mayfurther flow to the end portions 1 e and 1 e of the absorbent article 1.With the cover sheets 11, however, the longitudinal flows are stoppedand sealed by the pockets so that no excreted liquid leaks from the endportions 8 e of the ridges 8. Moreover, the cover sheets 11 hide the endportions 8 e of the ridges 8 to provide a beautiful appearance. Thecover sheets 11 are preferably made of a hydrophobic sheet having abasis weight (This may be referred to as “METSUKE” in Japanese measuringunit) of 20 g/m² or more, such as a spun-bond non-woven fabric, apoint-bond non-woven fabric, a non-woven fabric laminated withpolyethylene, or a film.

FIG. 8 is a perspective view showing a urine absorbing pad for anincontinent patient or old wearer (or absorbent article 1E), as aspecific example of the absorbent article of the invention; FIG. 9 is atransverse section of FIG. 8; and FIG. 10 is a section taken in thelongitudinal direction. The urine absorbing pad shown in FIG. 8 ispreferably used for a female wearer, and is used on the inner side of anouter wear material such as disposable diaper or underwear.

This urine absorbing pad is constructed, as shown in FIG. 9, of the backsheet 3, the surface structure 4 and the absorbent core 2 sandwichedtherebetween. The absorbent core 2 is formed by enveloping a mixture ofpulverized pulp and highly absorbent polymer (or SAP) with a tissuepaper 2 a.

The ridges 8, as formed of the surface sheet 5 of the surface structure4, are extended longitudinally of FIGS. 8 and 10 almost over the fulllength of the urine absorbing pad and are covered at their end portionswith the cover sheets 11 and 11. These cover sheets 11, the supportsheet 6 and the back sheet 3 are bonded to one another in the peripheralregion A having no absorbent core 2. The cover sheets 11 form thepockets as in the absorbent article shown in FIG. 7.

This urine absorbing pad is wholly curved, as shown in FIG. 10, to fitalong the crotch of the wearer by the elastic members 10 provided in theridges 8. As a result, a number of wrinkles are formed on the surfacesof the ridges 8.

Adjacent to the ridges 8 in the transverse direction, in addition, thereare formed stereoscopic gathers 16 and 16 for preventing the transverseleakage. With these stereoscopic gathers, it is possible to furtherprevent the transverse leakage of the excreted liquid. Thesestereoscopic gathers 16 and 16 are formed of liquid-impermeable sheetsinto the shape of band (or wall) which are provided with elastic members17 and 17, on their upper side edges thereof, and are bonded to theupper face of the support sheet 6, on their lower side edges. Thus, theabsorbent article 1E is provided with the stereoscopic gathers 16 and 16which rise toward the wearer. Here, longitudinal end portions of thestereoscopic gathers 16 and 16 are hidden like the end portions of theridges 8 by the cover sheets 11 and 11.

Here, the absorbent article of the invention can be used as not only adisposable diaper and an incontinent pad but also a sanitary napkin. Inthis case, the entire shape of the absorbent article can be variablymodified according to the applications. For example, it may be modifiedto have a rectangular top plan shape.

As has been described hereinbefore, the absorbent article of theinvention can bring its surface structure into close contact with thecrotch to prevent the leakage. Moreover, the absorbent article havingthe ridges of the invention can be freely deformed according to theindividual differences of the crotch so that it can fit the skin of thewearer to prevent the leakage more.

In the foregoing specification, the invention has been described inrelation to preferred embodiments and many details have been set forthfor the purpose of illustration. It will be apparent to those skilled inthe art that the invention is susceptible to additional embodiments andthat certain of the details described herein can be varied considerablywithout departing from the basic principles of the invention.

Further, ‘comprises/comprising’ when used in this specification is takento specify the presence of stated features, integers, steps orcomponents but does not preclude the presence or addition of one or moreother features, integers, steps, components or groups thereof.

What is claimed is:
 1. An absorbent article comprising: a surfacestructure having a liquid-permeable surface sheet located on aliquid-receiving side; a back sheet; and an absorbent core sandwichedbetween the surface structure and the back sheet, wherein, in an areaincluding at least a centerline extending in a longitudinal direction ofthe absorbent article, the surface sheet is corrugated to form recessesand ridges extending in the longitudinal direction and alternating witheach other in a transverse direction perpendicular to the longitudinaldirection, the ridges are given an elastically shrinking function in thelongitudinal direction at least at their crests or vicinities thereof sothat the surface structure is formed into a curved shape, and thesurface structure further comprises a liquid-permeable support sheetlocated between the surface sheet and the absorbent core and bonded tothe recesses of the surface sheet, wherein cover sheets are provided tocover longitudinally opposite end portions of the ridges, respectivelyand each cover sheet is dimensioned to have a transverse size largerthan that of the area where the ridges are formed, and is bonded to thesupport sheet to open inwardly of the absorbent article.
 2. An absorbentarticle according to claim 1, wherein elastic members extending in thelongitudinal direction are attached to the crests of the ridges of thesurface sheet to thereby give the elastically shrinking function.
 3. Anabsorbent article according to claim 1, wherein ridges in a centerregion including the longitudinally extending centerline are differentin height from other ridges in two side regions outside of the centerregion.
 4. An absorbent article comprising: a surface structure locatedon a liquid-receiving side; a back sheet; and an absorbent coresandwiched between the surface structure and the back sheet, the surfacestructure including a liquid-permeable first surface sheet, aliquid-permeable second surface sheet underlying the first surfacesheet, and a liquid-permeable support sheet located between the secondsurface sheet and the absorbent core, wherein, in an area including atleast a centerline extending in a longitudinal direction of theabsorbent article, the first and second surface sheets are corrugated toform recesses and ridges extending in the longitudinal direction andalternating with each other in a transverse direction perpendicular tothe longitudinal direction, respectively, so that the second surfacesheet has inner ridges each confined in a corresponding ridge of thefirst surface sheet, the support sheet is bonded to the recesses of thefirst and second surface sheets, and wherein elastic members extendingin the longitudinal direction are attached to crests of the inner ridgesof the second surface sheet to give an elastically shrinking function inthe longitudinal direction so that the surface structure is formed intoa curved shape.
 5. An absorbent article according to claim 4, whereincover sheets are provided to cover longitudinally opposite end portionsof the ridges, respectively.
 6. An absorbent article according to claim5, wherein each cover sheet is dimensioned to have a transverse sizelarger than that of the area where the ridges are formed, and is bondedto the support sheet to open inwardly of the absorbent article.
 7. Anabsorbent article according to claim 4, wherein each ridge of the firstsurface sheet is spaced apart from the corresponding inner ridge of thesecond surface sheet confined therein.